[GB SISSON]

With 5 lb pressure I immediately found the culprit. A deep pit all by itself. I found a corresponding pit on the cab floor under the tank. It appears that something like a tool or a nut fell between them years ago. I sanded with 40 grit, drilled a few tiny holes through the pit for tooth, wiped with acetone and covered the area with fuel proof epoxy paste, squeege'd in a 6"x12" piece of fiberglass cloth then another dose of epoxy wetting out the cloth fully. I will drive with a 12 gallon poly outboard tank plumbed into the bed for a week till the epoxy gets fully cured.
I will reinforce the seat frame and perhaps make a 1/2" spacer around the seat frame for added insurance. Ok, I can now proceed with the original topic at hand..... Thank you for your patience!